Planographic printing plate



May 12, 1936.- w. 'r. HAGELIN PLANOGRAPHIC PRINTING PLATE Filed May .26, 1934 Patented May 12, 1936 UNITED STATES rmnodaarmo ram'rma PLATE a William T. fiatelin, Cleveland, Ohio, assignor to Multimph p y, Wilmins o poration of Delaware n, M, a cor-' Application May 2 6, 1934, Serial No. 727,671

2 Claims. (Cl. fill-401.1)

This invention relates to improvements in planographic printing plates and it comprises a planographic printing plate having a metallic surface, preferably zinc, characterized by crepelike irregularities generally rounded in cross-sectional contour.

, So far as I am aware, all metallic planographic printing plates have heretofore been prepared for use by abrasive attrition of the printing surface 10 whereby a multiplicityof intercrossing abraded scratches finally eliminate in its entirety the original surface and leave in its stead a vast number of minutepeaks and valleys. The purpose of the so-produced grain is to increase the area of contact between the metal and the dampening fluid and to provide minute traps for the latter and thus prevent its entire displacement by the rolling action .of the ink rolls. The sharp peaks or apices of abrasively produced grain are objectionable in that they tend, in the non-printing areas, to cut through the filmof dampening fluid under the pressure exerted by the ink rolls and to thus become contaminated with ink.

It is an object of this invention to provide a metallic planographic printing surface characterized by crepe-like irregularities of generally rounded cross-sectional contour." Another object is to provide a metallic planographic printing surface. and preferably a zinc surface, having a 80 multiplicity of minute depressions bounded by prominences of generally rounded cross-sectional contour and substantially free from sharp apices. Still another object is to provide a multiplicity of depressions in a metallic planographic printing surface, bounded in one direction and on opposite sides by prominences of generally greater height than that of the prominences bounding said depressions in a direction normal to said first direction, whereby moisture is more effectively re tained in said depressions when the ink rolls transverse the printing surface in said first direction. Other objects and advantages will appear from an examination of the drawing in the light of the following description.

As an aid to visualization of the type of surface which I have discovered to be particularly useful for planographic printing, reference is had to the drawing in which:

Fig. 1 is a somewhat schematic plan view of a small area of a-rolled zinc r011, suitable for the purpose of this invention, as seen by angularly incident light at a magnification of circa x300 diameters; and

Fig. 2 is a cross section thereof illustrating the relative contour of the prominences and depresto a minute creping of the metal surface. More detailed inspection reveals the fact that the crepe effect is produced by irregular short rows of metal proininences of generally rounded but irregular contour. These rows A of metal prominences are separated by valleys or depressions B of irregular depth. ,The rows of ,prominences and of the valleys extend in a general longitudinaldirection transverse to that direction along which the foil traversed the compression rolls. And there is a marked general parallelism between the several crests and the corresponding valleys.

I have discovered that a creped surface such as is herein described is particularly well suited to planographic printing. One of the advantages of this creped surface is that the metal prominences are of generally rounded contour and devoid of sharp apices. Another advantage is that when the ink rolls traverse a dampened planographic plate, having the creped surface of this invention, in a direction normal to the general axis of the valleys or depressions, the dampening moisture is more effectively retained by the depressions than it is by an abrasively grained surface under otherwise like conditions.

For planographic printing with a dampening solution containing eight to ten per cent glycerin 35 and therefore having a correspondingly higher Under these conditions the average difference in level is about ten to twelve microns. For some purposes a crepe of about twice the above dimensions may be satisfactorily utilized and when a. very fine grain is, desired, as when printing very fine half tones on highly glazed paper, a crepe of somewhat less than half the above dimensions may be satisfactorily used.

I claim:

1. A planographic printing plate having a metallic printing suriace consisting of a multiplicity of depressions bounded by prominences generally rounded in cross-sectional contour and substantially free from sharp apices, said depressions and prominences extending in a generallongitudinal direction the prominences at opposite sides of the depressions being generally greater in heiyht than the prominenees at the 10 ends of the depressions.

2. A planographic' printing plate having a metallic printing suriace consisting of a multiplicity of depressions bounded by prominences generally rounded in cross-sectional contourtand substantially tree trom sharp apices, said depressions and proinineuces extending in a general longitudinal direction, the depressions and crests of the prpminences' being in general parallelism.

WILLIAM T. HAGELIN. 10 

